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Molecular Basis of Inheritance question

2005 · Q67
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Molecular Basis of Inheritance question

2005 · Q67

NEETBiologyMolecular Basis of InheritanceMCQ+4 / −1
E. coli cells with a mustard z gene of the lac operon cannot grow in medium containing only lactose as the source of energy because -
  1. A
    They cannot transport lactose from the medium into the cell
  2. B
    They cannot synthesize functional beta galactosidase
  3. C
    In the presence of glucose, E. coli cells do not utilize lactose
  4. D
    The lac operon is constitutively active in these cells
View written solutionFree

Correct answer: B

Operons are segments of genetic material which function as regulated unit or units that can be switched on and switched off. An operon consists of one to several structural genes. (Three in lac operon)
These are genes which produce mRNAs for forming polypeptides / proteins / enzymes. Z (produces enzyme β galactosidase for splitting lactose into glucose and galactose). Y (produces enzyme galactoside permease required in entry of lactose) A (produces enzyme thiogalactoside trans- acetylase).
The three structural genes of the operon produce a single polycistronic mRNA.

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